1. Technical Field
The present invention is directed to a three-way valve adapted to selectively control the flow of fluid between a fluid supply, a load device and a drain.
2. Background Art
Three-way valves have long been used for controlling fluid flow in a variety of air and hydraulic systems, particularly fuel systems. Such three-way valves often control the passage of fluid under high pressure from a source to a load device and selectively interrupt the flow of pressurized fluid while simultaneously connecting the load device to a substantially unpressurized drain. Typically, a three-way valve includes a valve housing having first, second and third valve passages interconnected by an internal valve chamber containing two valve seats and a valve member movable by an actuating device connected to the movable valve member to control fluid flow among the three valve passages by moving between
(1) a first position in which the movable valve member engages a first one of the valve seats to isolate a first one of the valve passages from the internal chamber while allowing fluid communication between the second and third valve passages through the second valve seat and internal chamber, and
(2) a second position in which the movable valve member engages the second valve seat to isolate a second one of the valve passage while allowing fluid communication between the first and third valve passages through the first valve seat and internal chamber.
As is well recognized, both valve manufacturers and designers of components incorporating valve assemblies continually strive to minimize the size, weight and cost of valve assemblies while maintaining the high operating requirements demanded for controlling the flow of very high pressure fluids. Thus, the above-discussed three-way valve assembly requires a valve assembly including an actuator assembly, a movable valve member and a floating pin which are operatively positioned relative to one another to minimize the size and weight of both the actuator assembly and the entire valve assembly while permitting a simple connection between the actuator and the valve element. Also, it is important to design a valve assembly capable of being operated by a conventional, "off-the-shelf" actuator assembly thereby eliminating the costs involved in procuring a specially designed actuator assembly.
A known type of three-way valve is the "pin-within-a-sleeve" design. For example, both U.S. Pat. Nos. 3,689,782 issued to Monpetit and 5,038,826 issued to Kabai et at. disclose a "pin within a sleeve" type three-way valve using a high speed solenoid actuator which provides fast response time and the ability to handle very high fluid pressures. These valves include a hollow movable valve member having a floating inner pin telescopingly received within the hollow movable valve member. In an advanced position, the hollow movable valve member is biased into engagement with a first valve seat formed in the surrounding valve housing and engaged by of the movable valve member. In a solenoid retracted position, the movable valve member is biased against the floating inner pin to open the first valve seat and close a second valve seat located within the hollow movable valve member and positioned to be engaged by one end of the floating inner pin. While the "pin-within-a-sleeve" offers fast response time and the ability to handle very high pressures, certain design problems remain unsolved.
For example, in the Monpetit and Kabai valves, as with most three-way valves, the actuating device, i.e. a solenoid assembly, used to initiate the movement of the movable valve member between the first and second positions, is mounted on the valve housing adjacent, and operatively connected, to one end of the movable valve member. In addition, the floating pin is positioned in the valve cavity formed in the movable valve member immediately adjacent the same end of the movable valve member as the actuating device. The positioning of the pin on the same side of the movable valve member as the actuating device both complicates the connection of the movable valve member to the actuating device and increases the size of the actuating device. For example, when a solenoid actuator is used, the armature of the solenoid must be sized to fit around both the pin and movable valve member. Moreover, since the pin acts as a valve seat which is impacted by the movable valve member, hundreds of times per minute in many applications, the pin must be sufficiently supported by a rigid body capable of withstanding these conditions. However, in the Mortpetit and Kabai valves, the solenoid assembly housing supports the pin therefore requiring more attention to be given to the design of the solenoid housing possibly resulting in a larger, heavier more expensive actuator.
The disadvantages associated with positioning the floating pin between the movable valve member and actuating assembly are exacerbated in other valve designs which require other valve components such as adjustable stops for the floating pin to be positioned adjacent the actuating assembly.
Therefore, there exists a need for a "pin-within-a-sleeve" type three-way valve having a floating pin located on the side of valve opposite the actuating assembly.